【摘要】：延邊地區(qū)位于華北克拉通、興蒙造山帶和俄羅斯遠東錫霍特-阿林活動大陸邊緣之間,自古生代以來經歷了古亞洲洋、古太平洋甚至太平洋板塊俯沖作用的影響,這些不同時期的大洋俯沖、消減導致了區(qū)域上發(fā)生了強烈的地殼增生和改造作用,是探討大陸地殼增生、改造、再循環(huán)甚至置換作用的天然實驗室�；◢弾r作為地殼的熔融產物,勢必記錄了區(qū)域地殼的形成和演化過程。論文選擇延邊地區(qū)廣泛發(fā)育的晚古生代-早白堊世花崗巖為研究對象,通過巖石學、主、微量元素、Sr-Nd同位素以及鋯石原位/微區(qū)Hf-O同位素的聯(lián)合研究,取得了以下主要研究成果和進展。(1)綜合的花崗巖元素-同位素對比結果顯示延邊地區(qū)以富爾河-古洞河斷裂為界可以劃分為南、北兩個巖區(qū)。在北區(qū),白堊紀之前形成的花崗巖顯示虧損、年輕的源區(qū)特征(εNd(t)=㧟0.1~㧏3.8,平均值為2.4;TDM2=691~976 Ma,平均值為795 Ma;鋯石εHf(t)=㧟2.5~㧏14.6,平均值為㧏9.0,TDM2=330~1388Ma,平均值為666 Ma;δ18O=3.4~8.7‰,平均值為5.60±0.36‰),反映其熔融源區(qū)主要為新增生的年輕地殼組分。在南區(qū),白堊紀之前形成的花崗巖則顯示相對富集的物質組成特點(εNd(t)=㧟13.6~㧟0.6,TDM2=1004~2166 Ma;鋯石εHf(t)=㧟25.8~㧏8.5,TDM2=663~2906 Ma;δ18O=4.9~10.2‰),反映其熔融源區(qū)中存在古老再循環(huán)的華北克拉通地殼組分。(2)區(qū)域內花崗巖的熔融源區(qū)包含了至少三種地殼組分:古亞洲洋型增生弧地殼、古太平洋型增生弧地殼和華北克拉通古老再循環(huán)地殼。在古亞洲洋增生地殼組分中存在高鋯石εHf(t)(㧏11.5~㧏14.6)和低?18O(5.5‰)的端元,很可能為構造侵位于地殼深部的殘留高溫蝕變洋殼。(3)從二疊紀到白堊紀,北區(qū)花崗巖全巖εNd(t)和鋯石εHf(t)值隨著侵位年齡的變新而逐漸降低,而鋯石的?18O值顯示逐漸升高的趨勢,南區(qū)花崗巖的變化趨勢正好相反,在早白堊世兩區(qū)的Nd-Hf-O同位素組成趨于一致,反映先存于北區(qū)的古亞洲洋型增生弧地殼和南區(qū)的華北克拉通古老再循環(huán)地殼,在中生代期間遭受古太平洋板塊俯沖形成的新生弧地殼的強烈改造和置換作用。(4)延邊地區(qū)顯生宙的地殼演化可以劃分為四個演化階段:(a)290-250 Ma為古亞洲洋俯沖導致的地殼增生階段,巖石類型主要為高鉀鈣堿性花崗巖;(b)240-210 Ma為古亞洲洋俯沖板片斷離的陸內伸展階段,深部地殼發(fā)生重熔形成大量的堿性花崗巖;(c)190-160 Ma,古太平洋俯沖-改造階段,形成了大量高鉀鈣堿性花崗巖;(d)130-110 Ma,古太平洋俯沖后撤階段,形成了鈣堿性花崗巖和火山巖。
[Abstract]:The Yanbian area is located between the North China Craton, the Xingmeng orogenic belt and the active continental margin of Sikhot-Arlin in the Russian far East. Since Paleozoic, the Yanbian area has experienced subduction of the paleo-Asian ocean, paleo-Pacific and even Pacific plate. The subduction and subduction of the ocean in these different periods lead to strong crustal accretion and transformation in the region, which is a natural laboratory for the exploration of continental crustal accretion, transformation, recycling and even replacement. Granite, as the melting product of the crust, is bound to record the formation and evolution of the regional crust. The late Paleozoic and early Cretaceous granites widely developed in Yanbian area were selected as the research objects. The combined studies of petrology, main elements and trace elements such as Sr ND isotopes and zircon in situ / microregional Hf-O isotopes were carried out. The main research results and progress are as follows: (1) the comprehensive comparison of elements and isotopes of granite shows that Yanbian area can be divided into two rock areas in the south and north by Fuhe-Gudong River fault. In the northern region, pre-Cretaceous granites show depleted, young source characteristics (蔚 Nd (t)? 0.1? The average value of Ma, is 2.4TDM2TDM2O691 / 976 Ma, and the average value is 795 Ma; zircon 蔚 Hf (t)? 2.5? 14.6, average? The average value is 666 Ma; 未 18O=3.4~8.7 鈥，

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